WO98/00180 describes the use of freeze-dried sponges of collagen admixed with oxidized regenerated cellulose (ORC) for the treatment of chronic wounds. Such sponges must in practice meet stringent requirements of purity, sterility and non-antigenicity.
It has not hitherto been possible to provide sponges of collagen/ORC mixtures having high reproducibility and high tensile strength both when wet and when dry. In particular, collagen is prone to denaturation when it is sterilized by gamma-irradiation. Furthermore, collagen sponges tend to disintegrate rather rapidly in wound fluid, especially in the presence of collagenase enzymes. Whilst this problem can be diminished by chemical cross-linking of the collagen sponge using cross-linking agents such as glutaldehyde, the use of such cross-linking agents can give rise to problems of toxicity and antigenicity.